Renin

Clinical use

Investigation of disorders of aldosterone production, most commonly suspected primary hyperaldosteronism (also referred to as Conn’s syndrome) which is usually caused the presence of an adrenal adenoma, adrenal hyperplasia or less commonly an adrenal carcinoma.

Both aldosterone and renin are measured together as part of initial and subsequent investigations (both aldosterone and renin can be measured on the same specimen).

Measurement of renin is also useful for monitoring mineralocorticoid replacement in conditions such as Addison’s disease and Congenital adrenal hyperplasia.

Background

Aldosterone in conjunction with renin and angiotensin plays an important role in regulating blood volume and systemic vascular resistance, which together influence cardiac output and arterial pressure. Renin is a proteolytic enzyme that is released into the circulation primarily by the kidneys in response to sympathetic nerve activation, renal artery hypotension and reduced sodium delivery to distal tubules in the kidneys. Renin cleaves angiotensinogen forming angiotensin-I, which in turn is converted to angiotensin-II (by Angiotensin converting enzyme) which stimulates aldosterone release from the adrenal glands.

Reference ranges

0.3 – 2.2nmol/L/h

Patient preparation

The Endocrine Society guidance recommends that prior to taking specimen for aldosterone/renin:

In the 2 weeks before testing, withdraw beta-blockers and alpha-2-agonists
If present, attempt to correct hypokalaemia (potassium ideally within the reference range)
Encourage liberal salt (sodium) intake in the days before testing
In the 4 weeks before testing, withdraw medications that can significantly affect ARR (e.g. amiloride, potassium wasting diuretics, spironolactone)

Withdrawing medications & beta-blockers

Only do if safe to do so; alternative non-interfering agents may be considered instead.

Specimen requirements

EDTA (purple top) tube

Special requirements

This should be transported to the laboratory within 30 minutes at room temperature. Specimens should NOT be transported on ice, as this will cause inaccurate renin measurements.

Minimum volume

3ml

Limitations/Restrictions